This invention relates to a telephone circuit distribution system and more particularly to a telephone distribution frame connector assembly having overload protector modules that provide line protection for inside plant equipment such as central office switching equipment.
Telephone distribution frame connectors, or panels as they are sometimes called, of the type having plug-in modules are generally known in the telephone art. In such connectors outside lines are connected to in-plant or central office switching equipment through protector modules which protect the inside equipment from damage due to over-voltage or over-current faults. These connectors or panels are mounted on distribution frames which are generally positioned close together. Space is often at a premium in such installations and accordingly, down-sizing or other space saving measures in the design of the connector assembly is a continuing objective.
A typical such connector assembly includes a module field which includes suitable connectors and terminals for receiving a plurality of overload protectors, a test field for receiving a test shoe to test the integrity of the connections, and an equipment field for terminating conductors from the inside plane equipment or central office switching equipment. The incoming lines are generally terminated either directly or through a cable stub to the terminals of the module field, which are respectively coupled to the appropriate terminals of receptacles which receive the respective overload protector modules. In this regard, a protector module is provided for each line pair being terminated in the module field. Accordingly, the protector modules are coupled between the incoming lines and the equipment field to provide a surge path to ground for the respective lines when an over-voltage fault or a current surge appears. In addition, the test field comprises a series of terminals coupled to the respective incoming lines. Thus, the connector assembly provides a protected interface between the incoming lines and inside plant lines and equipment, as well as providing a convenient place to test the various lines.
In typical arrangements of the foregoing types, wire conductors are routed between the various fields or groups of terminals in order to provide for the proper circuitry connections. These wire conductors may be wrapped or soldered or otherwise joined to the respective terminals, and they are generally routed behind the face of a module field "block" at which the modules are plugged in. Thus, these wire conductors are sometimes referred to as "back plane" wiring, that is, wiring which is internal to the connector assembly.
In a typical connector assembly, a conductive metallic frame member is utilized to mount the module field, test field and equipment field in the desired relative orientations, and also to mount the connector assembly to the main distribution frame. In this regard, one or more field "blocks" are generally formed as by molding or another suitable process, from a suitable moldable non-conductive material, such as a plastic material. Generally speaking, this mounting of the connector assembly to the distribution frame and orientation of fields is preferable so as to provide ready access firstly to the equipment field and test field and secondarily to the modules side of the module field. Accordingly, many connector assemblies orient or mount an equipment field block and/or test field block to form the front side of the connector assembly when mounted to the main distribution frame. The module side of the module field block is then mounted to one or the other side of the connector assembly, while a suitable access panel or cover plate is utilized to cover the back plane wiring thereon. The frame member and/or an additional wall portion of the module field block generally form a back or rear wall of the connector assembly. Accordingly, the connector assembly generally provides a housing or enclosure for enclosing the back plane wiring.
Many prior art connector assemblies provide a suitable ground path for ground points or terminals in the back plane, such as for the surge path for the overload protectors, directly to the metallic frame member which is in conductive contact with the distribution frame to provide what is generally called a "frame ground." However, in many installations it may be desirable to provide a current path to some ground point such as an "absolute" ground of a building or other installation which is isolated or separate from the frame ground. Such an alternate ground is generally referred to as an "isolated ground." Many connector assemblies heretofore in use have included permanent internal electrical connection to the frame ground. Such assemblies have generally been incapable of field modification to achieve such an isolated ground connection. Moreover, such connector assemblies have often been incapable of such ground path modification even during the manufacturing process, without substantial changes to the internal construction thereof, at great expense and time and labor.
An additional problem has arisen with respect to the integrity of the access panel or back plane cover panel in connector assemblies heretofore in use. In this regard, typical connector assemblies accommodate as many as 100 line pairs and hence mount as many as 100 associated overload protector modules. Accordingly, while access is necessary to the back plane wiring from time to time, the cover should nonetheless provide a relatively flat, secure closure, to prevent the ingress of wire clippings, dirt or the like when in service. Many connector assemblies heretofore in use have failed to provide a suitable cover and related assembly which may be reliably secured in this fashion and yet relatively simply removed for access to the back plane wiring.
A related problem has been the provision in some prior art assemblies of the test field block and equipment field block as a single integral piece to form the front surface of the connector assembly. In this regard, it is often desirable to provide equipment field blocks in a variety of configurations--for example, utilizing insulation displacement type connectors as opposed to wire wrap type of connectors, or the like. While such modification is generally not done in the field, it is relatively common to provide blocks containing the differing types of terminals for different installations. Heretofore, this has been relatively expensive, requiring duplicate tooling and parts costs for the test field portion of the integral block, which is usually of the same configuration in all installations.
Accordingly, it has been proposed to utilize separate blocks for the test field and equipment field. However, the test field comprises numerous relatively small terminal members and hence may present a relatively long, narrow surface. This block must also accommodate a removable mating connector or "test shoe" to accomplish testing of the connections. Accordingly, we encountered problems in maintaining the test field block and equipment field block in substantially flat condition, and in side-by-side alignment at all times, especially upon repeated engagement and disengagement of the test shoe. In this regard, we also encountered some problems of bowing out of the test field block, especially toward a medial portion thereof.